It is typical in many parts of the country that winter conditions create snow accumulations on roofs. As a result, ice forms on roof eaves and intersecting valley areas. A resulting ice dam forms when three conditions are present: 1) there is snow accumulation on a roof; 2) there is heat escaping from the building's interior that melts the accumulated snow; 3) outside ambient temperatures are below freezing, which will cause the melting snow from the heated area to re-freeze along a cold overhang of the roof.
Ice dams create standing water conditions above the ice formation that builds at a roof overhang. This standing water may leak into the structure and cause damage and dry rot. In addition, the accumulated weight of the ice and snow can be damaging to the roofing and the structure. For example, they can freeze to shingles and tear the shingles entirely off the roof.
Prior art that seeks to reduce ice dam formations includes heated edge elements and heat cable in various configurations, frequently in a zig-zag fashion. Heated edge elements, such as Tourangeau's U.S. Pat. No. 5,391,858, minimize the risk of ice dams best if there is a short overhang. The heating roofing panel can be sized to extend from the eave to virtually any point up the roof, therefore protecting against ice dam formations at the edge and up the entire overhang up to and beyond into the heated area of the building, no matter how large the overhang may be.
Exposed zig-zag configurations are a traditional installation method of heat cable, and can reach from the eave to several feet up the roof; however, much of the drip edge area remains unheated and can accumulate dangerous icicles and ice formations. Zig-zag heat cable is exposed to the elements, thus leading to accelerated ultraviolet degradation of the cable over time, and also requires a clip to be installed directly through the roofing, creating the risk of leaks. Zig-zag heat cable is sometimes attached to the top of metal roofing panels along eaves. This method fails because the exposed heat cable can be stripped off the roof with high winds or sliding snow. When attached with exposed fasteners, they penetrate and damage the roof, subsequently leaking and requiring ongoing maintenance. The heating roofing panel solves the zig-zag installation's ice formation problems by providing adequate heat along the eaves. Heating roofing panels also conceal the heat cable, make the assembly more aesthetically pleasing to the eye, while protecting it from degrading ultraviolet exposure, and damage from ice, wind, and snow.
Prior art, such as provided by Bylin Engineered Systems as well as Thermal Technologies, has attempted to provide heating roofing panel systems. One example of such systems includes a hat-channel shaped element mounted in a retrofit fashion along the eave edge of metal roofs. The hat channel has wide flanges that bear on the roof plane, and is sized to fit between the ribs of an existing metal roof. The flanges are attached with exposed fasteners through the existing metal roof. This attachment method uses exposed fasteners through an existing roofing system, and these fasteners may loosen, break their seal, and leak. The hat-channel is typically prepainted, but is only available in a small range of colors, so there is a great likelihood of an unsightly match between the existing roofing and the newly attached hat-channel. Further, the upper end of the hat-channel is exposed to roof drainage (exacerbating the leak risk problem) and is subject to being completely torn off when ice and now slides off the roof, destroying the hat-channel system and leaving the roof with exposed holes from the torn-off screws that had earlier secured the hat-channel to the roof.